Hydraulic lifting device



Nov. 22, 1966 s. EDERA HYDRAULIC. LIFTING DEVICE 2 Shets-Sheet 1 Filed July 12, 1965 INVENTOR.

EUGENE EOERA.

ATTORNEY E. EDERA HYDRAULIC LIFTING DEVICE Nov. 22, 1 966 INVENTOR.

El/G'A/E EOERA 2 Sheets-Sheet 2 Filed July 12, 1965 ATTORNEY United States Patent Office 3,286,985 Patented Nov. 22, 1966 3,286,985 HYDRAULIC LIFTING DEVICE Eugene Edera, Boynton Beach, Fla. (18 Midway Road, South Duxbury, Mass.) Filed July 12, 1965, Ser. No. 471,343 Claims. (Cl. 254-2) This invention relates to devices for'the lifting and transportation of pallets and heavy loads and more particularly to an improved hydraulic lift truck.

The presently known devices for lifting and transporting pallets and heavy loads are generally either pushed or pulled manually by means of a handle attached to the device. The devices are commonly referred to as pallet trucks and are known to include a hydraulic lifting unit, usually mounted on the steering assembly. The pump of the hydraulic unit is usually operated by an up and down movement of the handle. Such devices have generally been complex, unreliable in different positions and relatively inefiicient.

It is therefore the primary object of the present invention to provide a hydraulic pallet truck of a significantly improved, simple, low cost construction which reduces the efforts of operation, and make it adaptable to varying conditions, angular positions and floor levels.

These objects and advantages are achieved by a novel hydraulic pallet truck comprising a forward assembly the principal elements of which are: a casting which is mounted and pivots on a central shaft supporting the wheels and under carriage and also the lifting cylinder and its upper parts. The casting is pierced by three cylindrical bores into which fit a pump piston with suction and discharge, an overload and directional valve and a flow regulating or metering valve. The assembly is mounted onto a vertical member, which serves simultaneously as an attachment for the steering wheel axle at its lower extremity, a pressure cylinder for the lifting piston, and by means of its external upper thread, as a means for securing the assembly and at the same time locking into position a cylindrical chamber, which serves as an oil reservoir. The entire hydraulic system is sealed to prevent leaks and provide protection against atmospheric contamination.

The direction valve consists of a cylindrical ring, fixed into the casting and axially bored to three or more difl erent diameters in decreasing size from top to bottom. Perpendicular to each of the three diameters, a hole is drilled, intersecting the bores. Additionally, a groove is machined at the points of perpendicular intersection. The purpose of these grooves being the distribution of oil to the center bores regardless of the angular position of the valve with respect to drilled passages in the casting.

The bores communicate by non-return ball valves. One bore of the directional valve communicates at one point with the reservoir via an adjustable relief valve and indirectly with the lift piston through a metering valve. A second bore communicates with the pump. A third bore communicates directly with the reservoir. A shoulder between the first and second bores is sealed by a spring loaded ball which functions as a check valve. A shoulder separating the second and the third bores is sealed by a ball, free to move off its seat in the upward direction and impeding the flow of fluid in the opposite direction. Between the two balls is located a spacer. In the third bore is a pin which, when pushed progressively in the upward direction, can maintain the second ball off its seat. Further lifting of the second ball then causes the spacer to lift the first ball off its seat. These various positions of the balls serve to cause selective changes in the direction of fluid flow. The ball check valves may be placed in the open position by means of a pedal to lower the lifting mechanism.

Of particular importance, the pump piston is actuated by the handle. Within the pump piston is located a spring, which serves the dual purpose of returning the piston to the beginning of the suction stroke and of returning the handle to a vertical position.

A constant lowering speed metering valve controlling the return flow of fluid from the lifting cylinder to the reservoir is placed in the third bore. It consists of a ball constrained by a spring bearing against a threaded plug valve in such a manner as to open fully when liquid flows to the lifting piston and to partially close, functioning as a metering valve, when the liquid flow is reversed.

The steering assembly consists of two wheels mounted on a horizontal shaft and attached to the bottom of the vertical shaft at the lower extremity of the hydraulic unit by means of another horizontal shaft. This permits the free swiveling of the wheel axle and consequently the steering wheels, thus enabling the latter to adjust to variations in floor level. The details of the invention and operation will be more fully understood by reference to the accompanying drawings wherein;

FIGURE 1 is a view of the general appearance of the pallet truck, and

FIGURE 2 is a cross sectional view showing the details of the forward section of the pallet truck.

As shown in FIG. 2, a cylindrical shaft 1 functions as both the vertical pivot and vertical support for the forward carriage. Shaft 1 includes a shoulder 2 which serves as a support for casting 3 and has at its upper extremity a bore 4 and an exterior thread. A plug 5 having a hole 6 is screwed to the upper extremity of shaft 1. A piston rod 7 slides in bores 4 and 6. Its extreme upper limit is determined by a. cylindrical stop 8 at the top of the piston rod. An apron or plate 53 at the top is welded to the forked lifting platform shown in FIG. 1.

A cylindrical sleeve 9 resting on the casting 3 surrounds the upper part of shaft 1 and the lower face of plug 5 is in contact with this sleeve. A suitable pressure seal is inserted between the upper portion of sleeve 9 and the lower face of plug 5 and similarly at the lower extremity of sleeve 9. By screwing the female threaded section of plug 5 onto the male threaded portion of shaft 1 all members are secured to the casting 3 in an oil tight fashion. The space included between the inner diameter of the sleeve 9 and the outer diameter of shaft 1 constitutes a reservoir 10 partially filled with hydraulic fluid and air under pressure.

The casting 3 is pierced by three cylindrical bores, 11, 12, 13. Within bore 11 slides a piston 14 containing a spring within its inner bore. This piston is actuated by one end of lever 16, which is mounted on a shaft pivoting within a bore in casting 3. The other end 17 of the lever constitutes the attachment for the handle. At its upper extremity, the bore 11 has an orifice communicating with channel 19.

Within bore 12 is introduced a cylindrical body 20 maintained in its position by a cap 21. This cylindrical body is axially pierced by a series of bores 22, 2'3, 24, 25 and 26. Bow 22 communicates with bore 23 by means of a .ball check valve 27 and thus communicates with passage 28, shown broken, connected to reservoir 10.

The bore 23 communicates with passage 29 and bore 24, the diameter of which is smaller than that of bore 23, and with passage 19 and ball 30, which is restrained by a spring and rests on a seat consisting of a shoulder separating bores 23 and 24.

The bore 25, having a diameter smaller than that of bore 24, communicates with passage 31, shown broken, connected to the reservoir and a ball 32 resting on a seat constituted by a shoulder separating the two bores 24 and 25. A spacer 33 of predetermined size, moving freely in bore 24 rests by its own weight on ball 32 and maintains it on its seat. The bore 26 contains a pin 34 having longitudinal movements controlled by an eccentric pin mounted on shaft 36 which in turn is attached to a pedal 36a, shown in FIG. 1.

Passage 29 connects with bore 13. The latter introduces a cylindrical body 37 kept in position by a threaded plug 38. The cylindrical body is pierced axially by two bores 39 and 40, which communicate by orifice 41. In bore 39 is screwed a tapered plug 42, the end of which protrudes partially into orifice 41. The other side of orifice 41 is obstructed by ball check 43 which varies its clearance with orifice 41 according to the degree of protrusion of plug 42 into orifice 41. The lower extremity of bore 13 communicates with passages 44 and 45, drilled into shaft 1 and leading into bore 4. Passage 31, shown broken, communicates with an orifice 46 by means of passage 47. Reservoir 10 is sealed by a plug 48.

In operation the hydraulic fluid is admitted by orifice. 46 and the piston rod 7 is raised to its maximum height. The reservoir 10 is then sealed by plug 48, with the air in the reservoir being at atmospheric pressure. The various openings in casting 3 are sealed tight to maintain a closed hydraulic system not open to the atmosphere.

When piston rod 7 lowers, the level of liquid in reservoir 10 rises and the air within reservoir 10 is compressed. A reciprocal motion in the vertical plane causes the lever arm 16 to impart a vertical movement up and down to piston 14. The intake of liquid from reservoir 10 is via passage 31, raising ball 32 and spacer 33, then flowing into bore 11 by way of passage 19 and orifice 18. The discharge of the liquid arriving from bore 11 is through passage 19, lifting ball 30, passing through passage 29, depressing ball 43, entering bore 4 and raising piston 7. If the load to which piston rod 7 is subjected is too great, ball 27 rises and the liquid is by-passed to the reservoir 10 via passage 28.

When the pumping action is stopped, ball 30 prevents the liquid from backfiowing into bore 11. Spring which has been calibrated as being of sntficient force, applies pressure to lever arm 16 until the handle is returned to a vertical position. This 'has the advantage of reducing the overall dimensions of the unit and constitutes a safety measure to prevent accidents since handles often are left in the horizontal position. Raising of the front wheel structure supporting the forked loading platform shown in FIG. 1 is accomplished in a well known manner by mechanical linkages connected to the lifting cylinder to provide simultaneous even movement of the entire platform.

To lower the piston rod, foot pressure is applied to pedal 36a which causes shaft 36 to turn. The eccentric pin 35 raises pin 34, lifting ball 32 and spacer 33, which in turn lifts ball 30. This permits the liquid originating from passages 44 and 29 to traverse bores 23, 24 and to return to reservoir 10 via passage 31. Orifice 41 is partially obstructed by ball 43 to provide a variable pas sage for the fluid. The. variation can increase or decrease the lowering speed of the piston rod, consequently varying the lowering speed of the load platform and mechanical linkages. Once set, the lowering speed remains constant.

The simplicity of the elements and their disposition permit the economical construction of a hydraulic unit having three positions: (1) lifting, (2) neutral, with the steering handle free from hydraulic resistance, and (3) lowering-at a preselected constant speed by virtue of the.

constant lowering speed controlled by ball 43 and plug 42. In addition, the hydraulic unit is completely sealed and thus the unit may be placed in any position without danger of leakages, while also preventing the entrance.

of contaminating particles from the atmosphere A further advantageous feature is the swivelling axle of the forward carriage upon which the steering wheels are.

By virtue of their free movement, the wheels maintain themselves in constant contact with the ground even though it may be uneven. In addition, to modify the lifting height, it is-only necessary to change sleeve 9, plug 5 and piston rod 7 to similar pieces of greater length.

In the foregoing description a manually operated device has been described, however the hand operated pump may be replaced by a motorized pump at any time. While only a single embodiment has been illustrated, it is apparent that the invention is not limited to the exact form or use shown and that many other variations may be made in the design and configuration without departing from the scope of the invention as set forth in the appended claims.

What is claimed is:

1. A hydraulic lifting device comprising: a central vertical sha ft having a lifting cylinder; load supporting means connected to said cylinder for raising and lowering a load; a hydraulic fluid reservoir around said cylinder; means bores, a first bore having means for pumping said fluid, a

second bore having means for directing the flow of said fluid and providing relief for overloads, a third bore' having means regulating the flow of said fluid; means communicating between said bores, lifting cylinder and reser-.

voir to permit flow of said fluid therebetween and including a passage below said cylinder; means for reciprocating said pumping means to draw in fluid from said reservoir and to discharge said fluid into said passage below said cylinder to cause lifting thereof; and means lfOI returning said fluid from said cylinder to said reservoir to cause lowering of said cylinder.

2. The device of claim 1 including a rotatable lower extension of said vertical shaft; a pair of wheels on a first horizontal axle, said first axle being mounted on said lower shaft, and a second horizontal axle perpendicular to the first axle prvotally securing said wheels to said lower shaft.

3. The device of claim 1 wherein said second bore in-.

cludes a plurality of vertical coaxial bores of different diameters and having valves therebetween, one coaxial bore communicating with said first bore, a second. coaxial. bore communicating with said third bore and lifting cylin-.

der, and .a third coaxial bore communicating with 'said reservoir.

4. The device of claim 1 including a piston in said first bore and a lever pivotally secured to said casting and.

adapted to reciprocate said piston.

5. The device of claim 3 wherein said second coaxial.

bore includes a first resilient valve blocking the return of fluid from said cylinder to said reservoir during the. lifting of said cylinder.

6. The device of claim 4 including resilient means in.

cylinder and reservoir to permit the return of fluid to said reservoir during overload conditions.

8. The device of claim 7 wherein said second bore in-.

cludes a fourth coaxial bore having a passage communicating between said cylinder and reservoir, a third valve in said fourth coaxial bore controlling the return of fluid to said reservoir, a spacer between said first and third valves, and a linkage adapted to open said first and third valves and lower said cylinder.

9. The device of claim 8 wherein said third bore includes a fifth and sixth coaxial bore and an orifice therebetween, an adjustable tapered plug in said fifth coaxial bore and a fourth resilient valve in said sixth coaxial bore, said tapered plug bearing on said fourth valve to provide a constant flow of fluid through said orifice when lowering said cylinder.

10. The device of claim 8 wherein said linkage includes an axial pin with said fourth coaxial bore, a horizontal shaft mounted on said casting, an eccentric pin on said horizontal shaft to reciprocate said axial pin and a foot pedal to rotate said horizontal shaft.

References Cited by the Examiner UNITED STATES PATENTS 1,644,101 10/1927 Anderson 60-52 2,091,729 8/1937 Countryrnan 60-52 2,165,095 7/1939 Frechette 254-2 X 2,414,484 1/ 1947 Page 60-52 2,503,659 4/1950 Curtis 254-93 3,136,128 6/1964 Suter 60-52 3,188,107 6/1965 Quayle 254-2 X WILLIAM FELDMAN, Primary Examiner.

MILTON S. MEHR, Examiner. 

1. A HYDRAULIC LIFTING DEVICE COMPRISING: A CENTRAL VERTICAL SHAFT HAVING A LIFTING CYLINDER; LOAD SUPPORTING MEANS CONNECTED TO SAID CYLINDER FOR RAISING AND LOWERING A LOAD; A HYDRAULIC FLUID RESERVOIR AROUND SAID CYLINDER; MEANS SEALING IN SAID FLUID FROM THE ATMOSPHERE; A CASTING SECURED TO SAID SHAFT, SAID CASTING INCLUDING THREE VERTICAL PARALLEL BORES, A FIRST BORE HAVING MEANS FOR PUMPING SAID FLUID, A SECOND BORE HAVING MEANS FOR DIRECTING THE FLOW OF SAID FLUID AND PROVIDING RELIEF FOR OVERLOADS, A THIRD BORE HAVING MEANS REGULATING THE FLOW OF SAID FLUID; MEANS COMMUNICATING BETWEEN SAID BORES, LIFTING CYLINDER AND RESERVOIR TO PERMIT FLOW AND SAID FLUID THEREBETWEEN AND INCLUDING A PASSAGE BELOW SAID CYLINDER; MEANS FOR RECIPROCATING 